Electric power tool

Abstract

An electric power tool includes a brushless motor, a control unit configured to control power supply to the brushless motor, a rotary tool configured to be rotated by the brushless motor, a rotation speed detecting unit configured to detect a rotation speed of the brushless motor, a main switch configured to transmit, to the control unit, an ON/OFF signal for switching between driving and stopping of the brushless motor, and a mode switching unit configured to transmit, to the control unit, a mode switching signal for switching between multiple modes of rotation control of the brushless motor, the control unit is configured to perform the rotation control of the brushless motor in any one of the multiple modes including at least a high-speed mode and a low-speed mode.

The invention claimed is: 
     
       1. An electric power tool comprising:
 a brushless motor; 
 a controller configured to control power supply to the brushless motor, the controller including a detector configured to detect a load on the brushless motor; 
 a rotary tool configured to be rotated by the brushless motor; 
 a rotation speed detecting unit configured to detect a rotation speed of the brushless motor; and 
 a main switch configured for switching between driving and stopping of the brushless motor 
 wherein the controller is configured to perform the rotation control of the brushless motor in any one of the multiple modes including at least a high-speed mode and a low-speed mode, 
 wherein in the low-speed mode, the controller is configured to control the brushless motor to rotate at a constant rotation speed by duty ratio control, 
 wherein in the high-speed mode, the controller is configured to control the brushless motor to rotate at a constant duty ratio, 
 wherein in the low-speed mode, when the load detected is equal to or larger than a first predetermined value, the controller is configured to perform switching of the low-speed mode to the high-speed mode and increasing the rotation speed of the motor. 
 
     
     
       2. The electric power tool according to  claim 1 , further comprising:
 a battery pack which is removably attached and is configured to supply electric power to the brushless motor and the controller. 
 
     
     
       3. The electric power tool according to  claim 1 ,
 wherein detection of the load equal to or larger than the first predetermined value is performed based on predetermined one or combination of a current, a voltage, and a duty ratio. 
 
     
     
       4. The electric power tool according to  claim 1 ,
 wherein the predetermined duty ratio control includes control for gradually increasing a duty ratio to a predetermined duty ratio and then driving the brushless motor with the predetermined duty ratio. 
 
     
     
       5. The electric power tool according to  claim 1 ,
 wherein when a load equal to or smaller than a second predetermined value which is smaller than the first predetermined value for switching to the predetermined duty ratio control is detected in a state where the predetermined duty ratio control is performed, the controller is configured to gradually decrease the duty ratio and then control the brushless motor to rotate at a predetermined first rotation speed. 
 
     
     
       6. The electric power tool according to  claim 1 ,
 wherein the rotary tool is connected to an output shaft of the brushless motor through a deceleration mechanism, and 
 wherein in the low-speed mode, the controller is configured to be able to control the brushless motor such that a rotation speed of the rotary tool becomes constant in a range from 2,500 rpm to 3,500 rpm. 
 
     
     
       7. The electric power tool according to  claim 1 ,
 wherein the controller is configured to perform soft start control for gradually supplying a current at starting of the brushless motor. 
 
     
     
       8. The electric power tool according to  claim 1  further comprising a mode switching unit configured to transmit, to the controller, a mode switching signal for switching between multiple modes of rotation control of the brushless motor. 
     
     
       9. The electric power tool according to  claim 1 ,
 wherein the detector is a resistor for detecting a current of the brushless motor. 
 
     
     
       10. An electric power tool comprising:
 a brushless motor; 
 a controller configured to control power supply to the brushless motor, the controller including a detector configured to detect a load on the brushless motor; 
 a rotary tool configured to be rotated by the brushless motor; 
 a rotation speed detecting unit configured to detect a rotation speed of the brushless motor; and 
 a main switch configured for switching between driving and stopping of the brushless motor, 
 wherein the controller is configured to perform rotation control of the brushless motor in any one of multiple modes including at least a constant-speed control mode and a predetermined duty ratio control mode, 
 wherein in the constant-speed control mode, the controller is configured to control the brushless motor to rotate at a constant rotation speed by a duty ratio smaller than 100%, 
 wherein in the predetermined duty ratio control mode, the controller is configured to control the brushless motor to rotate by the constant duty ratio, 
 wherein in the constant-speed control mode, when the load detected is equal to or larger than a first predetermined value, the controller is configured to perform switching from the constant-speed control mode to the predetermined duty ratio control mode, and 
 wherein at least in a part of load range in the predetermined duty ratio control mode, the controller is configured to be able to drive the brushless motor at a speed exceeding the constant rotation speed. 
 
     
     
       11. The electric power tool according to  claim 10 ,
 wherein the load at which the constant-speed control is switched to the predetermined duty ratio control is set to such a threshold value that if the load exceeds the threshold value, an efficiency of the predetermined duty ratio control becomes higher than an efficiency of the constant-speed control, or is set to a value in the vicinity of the threshold value. 
 
     
     
       12. The electric power tool according to  claim 10 ,
 wherein when a load equal to or smaller than a second predetermined value is detected in a state where the predetermined duty ratio control is performed, the controller is configured to gradually decrease the duty ratio such that the rotation speed of the brushless motor becomes a predetermined rotation speed, and then perform the constant-speed control on the brushless motor at the predetermined rotation speed. 
 
     
     
       13. The electric power tool according to  claim 12 ,
 wherein the second predetermined value at which the duty ratio is decreased from the predetermined duty ratio control to the constant-speed control is smaller than the first predetermined value at which the constant-speed control is changed to the predetermined duty ratio control. 
 
     
     
       14. The electric power tool according to  claim 10 ,
 wherein the detector is a resistor for detecting a current of the brushless motor.